1. Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method thereof, and more specifically to a semiconductor device having a multi-layer interconnection structure for use in an integrated circuit, and a manufacturing method thereof.
2. Description of the Background Art
FIG. 23 and FIGS. 24 to 30 are schematic cross-sectional views that show the structure of a conventional semiconductor device having a multi-layer interconnection structure and a manufacturing method thereof, which are described, for example, on page 30 in xe2x80x9cElectronic Journalxe2x80x9d, December Issue, 1997.
Referring to FIG. 23, an etching stopper layer 115 made of, for example, SiN film (silicon nitride film) is formed on a lower-layer interconnection 114. On the etching stopper layer 115, an interlayer film 101 made of, for example, SiO2 film (silicon oxide film) is formed. On the upper surface of the interlayer film 101, a groove 102a that for filling with interconnection and a connection hole 101a that reaches the lower-layer interconnection 114 from the bottom surface of the groove 102a are formed.
A barrier metal 103 made of, for example, TaN (tantalum nitride) film is formed along the inner surface of the connection hole 101a and the groove 102a, and a Cu film 104 is formed so as to be embedded in the connection hole 101a and the groove 102a. The barrier metal 103 and the Cu film 104 constitute an upper interconnection.
Next, an explanation will be given of the manufacturing method of the conventional semiconductor device shown in FIG. 23.
Referring to FIG. 24, the etching stopper layer 115 and the interlayer film 101 are successively formed on the lower-layer interconnection 114 by a plasma CVD (Chemical Vapor Deposition) method.
Referring to FIG. 25, after photoresist has been applied to the interlayer film 101, this is exposed and developed to form a resist pattern 121a having a pattern of connection holes.
Referring to FIG. 26, the interlayer film 101 is subjected to a dry etching process using this resist pattern 121a as a mask. Thus, a hole 101a that reaches the etching stopper layer 115 is formed in the interlayer film 101. Thereafter, the resist pattern 121a is removed by ashing and a chemical treatment.
Referring to FIG. 27, after photoresist has been applied to the interlayer film 101, this is exposed and developed to form a resist pattern 121b having a pattern of grooves.
Referring to FIG. 28, the interlayer film 101 is subjected to a dry etching process using this resist pattern 121b as a mask to form a groove 102a used for interconnection in the interlayer film 101. Thereafter, the resist pattern 121b is removed by ashing and a chemical treatment.
Referring to FIG. 29, the etching stopper layer 115 exposed from the hole 101a is removed by the dry etching process so that one portion of the surface of the lower-layer interconnection 114 is exposed.
Referring to FIG. 30, a barrier metal 103 and a seed layer for a plating film are formed on the interlayer film 101. With respect to the barrier metal, a TaN film is used, and a Cu film is used as the seed layer. The TaN film 30 is formed with a thickness of 20 nm by, for example, a sputtering method, and the Cu film forming the seed layer is formed with a thickness of 200 nm by, for example, a sputtering method. Thereafter, Cu is deposited by an electrolytic plating method in a manner so as to fill the groove 102a and the connection hole 101a, thereby forming a Cu film 104.
Then, the Cu film 104 and the barrier metal 103 are abraded and removed by a chemical mechanical polishing method (CMP method) until the upper surface of the interlayer film 101 has been exposed, and allowed to remain only in the connection hole 101a and the groove 102a so as to form interconnection. The above-mentioned processes are repeated to form multi-layer interconnection.
Since the conventional semiconductor device having a multi-layer interconnection structure is designed as described above, the depth of etching of the hole 101a has a value that corresponds to the sum of the depth of the connection hole and the height of the interconnection, as illustrated in FIG. 26. For this reason, upon forming the hole 101a, an extremely deep etching process is required, and this etching has to be stopped by the thin etching stopper layer 115. Consequently, it is very difficult to carry out etching on the hole 101a, with the result that, due to a reduction in the margin of safety of the process, problems arise in which the etching finishes before the connection hole 101a has been completely opened, causing an insufficient opening or, in contrast, penetration occurs in the etching layer 115.
The insufficient opening causes insufficient connection in the connection hole 101a. Moreover, the penetration of the etching stopper layer 115 causes surface oxidation of the lower-layer interconnection 114, resulting in an increase in the connection resistance and insufficient connection. These problems have caused a problem of an extreme reduction in the yield of the multi-layer interconnection.
An object of the present invention is to provide a semiconductor device having a multi-layer structure and a manufacturing method thereof, which is possible to form a connection hole and a groove by using a simple process, and consequently to improve the yield as well as to reduce the number of processes and the production costs.
According to the present invention, there is provided a semiconductor device having a multi-layer interconnection structure in which a lower-layer interconnection and an upper-layer interconnection are laminated with an insulating film interpolated in between, wherein the insulating film has a groove filled with the upper layer interconnection on its upper surface, a connection hole for connecting the upper-layer interconnection and the lower-layer interconnection, and a photosensitive film.
In accordance with the semiconductor device of the present invention, the insulating film has a photosensitive property; therefore, after the insulating film has been exposed, this is developed so that a groove and a connection hole are formed. In this developing process, since only the photosensitive insulating film can be selectively removed, it is possible to prevent penetration through the stopper layer located beneath the photosensitive insulating film. Therefore, since the developing time and other conditions can be set without the need of taking the penetration of the stopper layer into consideration, it is possible to effectively prevent the insufficient opening. Consequently, it becomes possible to improve the yield and also to reduce the number of processes and the production costs.
Here, the photosensitive insulating film of the present invention refers to an insulating film whose solubility to a developing solution changes from a soluble state to an insoluble state or from an insoluble state to a soluble state, upon irradiation with light or energy particles.
In the above-mentioned semiconductor device, the insulating film preferably provided has a structure in which a lower-layer insulating film and an upper-layer insulating film that are exposed to mutually different wavelengths are laminated, and a connection hole is formed in the lower-layer insulating film and a groove is formed on the upper-layer insulating film.
With this arrangement, the connection hole and the groove are formed in a separate manner by changing only the wavelength of exposure light.
In the above-mentioned semiconductor device, the wavelength to which the lower-layer insulating film is exposed is set to be shorter than the wavelength to which the upper-layer insulating film is exposed.
With this arrangement, it becomes possible to form the connection hole and the groove by using fewer processes.
In the above-mentioned semiconductor device, the insulating film preferably has a structure in which a lower-layer insulating film and an upper-layer insulating film that have mutually different sensitivities are stacked, and a connection hole is formed in the lower-layer insulating film and a groove is formed in the upper-layer insulating film.
With this arrangement, it becomes possible to form the connection hole and the groove in a separate manner by changing only the dose of exposure.
In the above-mentioned semiconductor device, the sensitivity that the lower-layer insulating film is exposed is set to be lower than the sensitivity that the upper-layer insulating film is exposed.
With this arrangement, it becomes possible to form the connection hole and the groove by using fewer processes.
In the above-mentioned semiconductor device, the insulating film preferably has a structure in which a lower-layer insulating film and an upper-layer insulating film that are exposed to mutually different exposure sources are stacked, and a connection hole is formed in the lower-layer insulating film and a groove is formed on the upper-layer insulating film.
With this arrangement, it is possible to form the connection hole and the groove in a separate manner by changing only the exposure source.
In the above-mentioned semiconductor device, more preferably, the lower-layer insulating film is exposed to two kinds of exposure sources, and the upper-layer insulating film is exposed to any one of the two kinds of exposure sources.
With this arrangement, it becomes possible to form the connection hole and the groove by using fewer processes.
In the above-mentioned semiconductor device, the insulating film preferably has a structure in which a first photosensitive insulating film, an exposure source absorption film and a second photosensitive insulating film are stacked in succession, and a connection hole is formed in the first photosensitive insulating film and a groove is formed on the second photosensitive insulating film.
Since the exposure source absorption film is formed, only the second photosensitive insulating film as the upper layer can be exposed, while the first photosensitive insulating film as the lower layer is left unexposed. Thus, it is possible to form the connection hole and the groove in a separate manner.
Here, the exposure source absorption film in the present invention refers to an insulating film that has an absorbing body with respect to light having a specific wavelength or specific energy particles.
In the above-mentioned semiconductor device, more preferably, the insulating film is formed by a single layer.
Even when the photosensitive insulating film is formed by a single layer, the connection hole and the groove can be formed in a separate manner by changing the dose of exposure of the exposure light.
In the above-mentioned semiconductor device, more preferably, the connection hole is formed so as to be located only within an area below the groove.
With this arrangement, it is possible to prevent the formation area of the connection hole from sticking out from the area below the groove, and consequently to be able to reduce the interconnection intervals.
In the above-mentioned semiconductor device, more preferably, the width of the groove and the aperture width of the connection hole are set to be virtually the same, and the side wall of the groove and the side wall of the connection hole constitute a virtually continuous surface.
With this arrangement, it is possible to prevent the formation area of the connection hole from sticking out from the area below the groove, and consequently to reduce the interconnection intervals.
The manufacturing method of a semiconductor device of the present invention, which is a process for manufacturing a semiconductor device having a multi-layer interconnection structure in which a lower-layer interconnection and an upper-layer interconnection are laminated with an insulating film interpolated in between, is characterized in that, after the insulating film having a photosensitive property has been exposed, this is then developed so that a groove for filling with the upper-layer interconnection is formed on the upper surface thereof while a connection hole for connecting the upper-layer interconnection and the lower-layer interconnection is formed below the groove.
In accordance with the manufacturing method of a semiconductor device of the present invention, the insulating film has a photosensitive property; therefore, after the insulating film has been exposed, this is developed so that a groove and a connection hole are formed. In this developing process, since only the photosensitive insulating film can be selectively removed, it is possible to prevent penetration through the stopper layer located beneath the photosensitive insulating film. Therefore, since the developing time and other conditions can be set without the need of taking the penetration of the stopper layer into consideration, it is possible to effectively prevent the insufficient opening. Consequently, it becomes possible to improve the yield and also to reduce the number of processes and the production costs.
In the above-mentioned manufacturing method of a semiconductor device, the insulating film is preferably formed to a structure in which a lower-layer insulating film and an upper-layer insulating film that are exposed to mutually different wavelengths are laminated, and the lower-layer insulating film is exposed by a first wavelength to form a connection hole therein, and the upper-layer insulating film is exposed by a second wavelength that is different from the first wavelength to form a groove therein.
With this arrangement, the connection hole and the groove are formed in a separate manner by changing only the wavelength of exposure light.
In the above-mentioned manufacturing method of a semiconductor device, more preferably, the first wavelength is shorter than the second wavelength.
With this arrangement, it becomes possible to form the connection hole and the groove by using fewer processes.
In the above-mentioned manufacturing method of a semiconductor device, the insulating film is preferably formed to a structure in which a lower-layer insulating film and an upper-layer insulating film that have mutually different sensitivities are stacked, and the lower-layer insulating film is exposed by a first dose of exposure to form a connection hole therein, and the upper-layer insulating film is exposed by a second dose of exposure that is different from the first dose of exposure to form a groove therein.
With this arrangement, it becomes possible to form the connection hole and the groove in a separate manner by changing only the dose of exposure.
In the above-mentioned manufacturing method of a semiconductor device, more preferably, the first dose of exposure is greater than the second dose of exposure.
With this arrangement, it becomes possible to form the connection hole and the groove by using fewer processes.
In the above-mentioned manufacturing method of a semiconductor device, the insulating film is preferably formed to a structure in which a lower-layer insulating film and an upper-layer insulating film that are exposed to mutually different exposure sources are stacked, and the lower-layer insulating film is exposed by a first exposure source to form a connection hole therein, and the upper-layer insulating film is exposed by a second exposure source that is different from the first exposure source to form a groove therein.
With this arrangement, it is possible to form the connection hole and the groove in a separate manner by changing only the exposure source.
In the above-mentioned manufacturing method of a semiconductor device, the insulating film is preferably formed to a structure in which a first photosensitive insulating film, an exposure source absorption film and a second photosensitive insulating film are laminated in succession, and a first exposure forms a connection hole in the first photosensitive insulating film and a second exposure forms a groove on the second photosensitive insulating film.
Since the exposure source absorption film is formed, only the second photosensitive insulating film as the upper layer can be exposed, while the first photosensitive insulating film as the lower layer is left unexposed. Thus, it is possible to form the connection hole and the groove in a separate manner.
In the above-mentioned manufacturing method of a semiconductor device, more preferably, the insulating film is formed by a single photosensitive insulating film.
With this arrangement, it is possible to simplify the structure and the manufacturing processes.
In the above-mentioned manufacturing method of a semiconductor device, more preferably, the single photosensitive insulating film is exposed by a first dose of exposure to form a connection hole therein, and the single photosensitive insulating film is also exposed by a second dose of exposure that is different from the first dose of exposure to form a groove therein.
With this arrangement, the groove and the hole can be formed even in the single photosensitive insulating film.
In the above-mentioned manufacturing method of a semiconductor device, more preferably, the first dose of exposure is greater than the second dose of exposure.
With this arrangement, the connection hole and the groove can be formed by using fewer processes.
In the above-mentioned manufacturing method of a semiconductor device, more preferably, the exposing process for the groove and the exposing process for the connection hole are carried out at the same time.
With this arrangement, the connection hole and the groove can be formed by using fewer processes, and it is possible to form a structure in which the groove and the connection hole are completely overlapped with each other, and consequently to be able to narrow the intervals of the interconnections.
In the above-mentioned manufacturing method of a semiconductor device, more preferably, the exposing process for the groove and the exposing process for the connection hole are carried out at the same time so that the connection hole is formed so as to be located only at a position within an area below the groove.
With this arrangement, it is possible to prevent the formation area of the connection hole from sticking out from the area below the groove, and consequently to reduce the interconnection intervals.
In the above-mentioned manufacturing method of a semiconductor device, more preferably, the width of the groove and the aperture width of the connection hole are set to be virtually the same, and the side wall of the groove and the side wall of the connection hole constitute a virtually continuous surface.
With this arrangement, it is possible to prevent the formation area of the connection hole from sticking out from the area below the groove, and consequently to be able to reduce the interconnection intervals.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.